Leucism is a very unusual condition whereby the pigmentation cells in an animal or bird fail to develop properly. This can result in unusual white patches appearing on the animal, or, more rarely, completely white creatures.

Albinism is a different condition. The easiest way to tell the difference between the two is that in albinism the eyes are usually pink or red, and albinism affects the entire animal, not just patches.

This occassionaly causes very excited biologists to think they have discovered a new species, when in fact leucism is the cause of the unusual markings they have seen.